Brandon Jennings is one step closer to marrying girlfriend Lashontae Heckard — because the ex-video vixen has filed papers to END her domestic partnership with another woman … TMZ Sports has learned.

There are rumblings that Jennings and Heckard are engaged — but fact is, Heckard can’t legally tie the knot until she terminates her relationship with a woman named Monique Blanton … who she domestically partnered up with back in 2008.

According to court docs filed in L.A. County Superior Court, Lashontae took Monique’s last name — so, their relationship appears to have been more than just a way to save on taxes.

Either way, Tae notes in legal docs that she and Monique separated in 2011 … citing irreconcilable differences.

In the docs, Tae checked the box to legally restore her last name to Heckard — clearing the way to become a Jennings … if, in fact, she and Brandon trade “I dos.”